He is the first man to land on the moon.

[Sitifan]

Both finite and non-finite clauses may follow superlatives. The non-finite clauses have a similar function to relative clauses:
That’s one of the best films I’ve ever seen.
She’s the youngest swimmer to qualify for the Olympics.
They were the fittest team finishing the course.
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The above is quoted from Cambridge Grammar of English.
The following sentences are all acceptable, aren't they?
1. He is the first man who landed on the moon.
2. He is the first man to land on the moon.
3. He is the first man landing on the moon.
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Thank you very much for your reply.

[Jamie (K)]

They are all acceptable, but 3 would probably not be used for a historical event, but for something that is happening right at the moment.